On the trolley wire that supplies a power to a car of an electric railroad or railway, contact with a pantograph current collector occurs each time the car passes.
Because of this, the trolley wire is gradually worn out during an operation of the electric railway car, and if a replacement is not made, a rupture or breaking finally occurs and causes an accident.
A wear limit is then set for the trolley wire. By using the wear limit as an index of a change of the trolley wire, the trolley wire is changed and safety of the electric railway car is secured.
As a method of measuring the wear of the trolley wire, there are mainly two methods; one is a method that directly measures a thickness of the trolley wire, the other is a method that calculates a width of a trolley wire worn portion and transforms the wear width into the thickness of the trolley wire.
As the method measuring the width of the trolley wire worn portion, of the above methods, there is a method that measures the trolley wire worn portion by applying sodium lamp or laser light (refer to a Non-patent Document 1).
This is the one that uses the following relation; a lower portion of the trolley wire is a round gourd in shape, and, as the trolley wire is shaved by the wear and becomes flatter, the width of the shaved portion becomes wider. Then, the thickness of the shaved portion of the trolley wire is transformed from the wear width.
As the measuring method of the trolley wire worn portion, positions of a light source and a line sensor of a light receiving part are precisely adjusted so that a reflected light from the trolley wire worn portion is received with regular reflection when applying the sodium lamp or laser light from the light source, and the trolley wire worn portion is changed into a whiteout state by way of capturing and imaging an intense light by the regular reflection, then the width of the trolley wire worn portion is measured from a width of the whiteout portion which receives the intense light. This manner is a non-contact manner, thus a high speed operation is possible.
However, this manner is susceptible to noises such as a clamp that pinches the trolley wire and a structure which appears on the background. Further, in a case where a wrong measurement result is obtained due to some noises, there is no way to verify the result. Then, with regard to the portion of the problem as the wear of the trolley wire, it is verified using the method directly measuring the thickness of the trolley wire in the end. In addition, it is required that the regular reflection is received by precisely adjusting the positions of the light source and a light receiving device.
For these problems, in “TROLLEY WIRE ABRASION MEASURING DEVICE BY IMAGE PROCESSING (Patent Document 1)”, there is no need to provide a special light for illumination, such as the sodium lamp and laser light, and a normal light can be used. Furthermore, the measurement can be carried out without requiring the precise adjustment of the position of the light source.
However, there is a problem in which unevenness of the reflected light that falls on or strikes the line sensor appears and it is difficult to create a uniform lighting condition.
Patent Document 1: Japanese Patent Application Kokai Publication No. 2006-248411
Non-patent Document 1: “Development of Electric-Train Overhead Wire Detecting and Measuring Device Using Road/Rail Vehicle”, 114th Railway Technical Research Institute monthly report summary <Home page>http://www.rtri.or.jp/infoce/getsurei/1998/Getsu09/g114—5.html